EP1014100B1 - Appliance for detecting an open circuit in an electrical line, in particular a telephone line - Google Patents

Abstract

The detection system includes a bi-stable relay (4) having a movable change of state part (5) designed to be activated by at least two windings (9,10) and whose exterior connection terminals (6,7,8) are connected to a transistor (11) which delivers an electrical pulse to the winding at the moment of fall in voltage on the line. This voltage fall causes the relay (4) to move into a first state. The system has another transistor (12) which delivers an electrical pulse to the winding when the line is cut, the pulse is produced by a capacitor (13) which is charged by the line so that the relay (4) is moved into a second state. The system has means for delivering a pulse to the second winding (10) which includes a capacitor (21) used to delay for a pre-determined time the electrical pulse with respect to the start of the line cut off and to only deliver the pulse if the line cut off persists for a time at least equal to the delay.

Description

The present invention relates to a device for detecting power line cut, including a telephone line.

Telephone line break detection devices currently used include a monostable relay that is in the state stuck in the presence of the voltage of the telephone line and starts to sound stable state taken off after a determined period of absence of tension telephone line. Such detection devices require the use of an external power supply, US Pat. No. 3,887,824 discloses a link monitoring circuit for central office of telescription, which recognizes a line break.

The present invention, according to claim 1, relates to a detection device of a power line that does not use such external power supply.

The device for detecting a cut of a power line in particular a telephone line, includes a bistable relay comprising a movable state change member capable of being activated by at least one coil and whose connection pads are likely to be connected to external means, means for delivering an electrical pulse to said coil during energizing said power line and produced by the energy electrical system of the latter, in order to place said relay at a first state, means for delivering an electrical pulse to said coil during the cutting of said power line and produced by means electrical energy stored by the power line, in order to placing said relay to a second state.

According to a variant of the invention, said means for delivering a pulse electrics to the second coil preferably comprise means to delay by a predetermined time this electrical pulse by report at the beginning of a power line break and for no deliver this electrical impulse only if this break is maintained for a duration at least equal to the said period.

According to another variant of the invention, the detection device comprises preferably control means acting on said means for delivering said electrical pulses according to the value of the voltage of said electric line with respect to a reference value.

According to another variant of the invention, said means for delivering said electrical pulses preferably comprise two transistors whose emitters are connected to one another and whose collectors are respectively connected to a terminal of a first and second coils, said transmitters being connected to one of said poles via an electrical energy storage capacitor and the basics said transistors being connected to the output of a comparator of command likely to take a first state when the voltage of the power line is greater than a predetermined value and a second state when the voltage of the power line is less than this predetermined value, the other terminals of said coils being connected to the poles of said power line, so that when the output of said comparator goes to its first state, said poles are connected through one of said coils, one of said transistors and said capacitor, the electrical pulse being delivered to this coil during the charging of this capacitor, and when the output of said comparator goes to its second state, the charged capacitor is discharge through the other transistor and the other coil, the electrical pulse being delivered to this other coil during the discharging said capacitor.

According to another variant of the invention, said means for supplying said electrical pulses comprise two transistors whose emitters are connected to each other and to a terminal of said coil and whose collectors are respectively connected to the poles of the line electrical connection, the other terminal of said coil being connected to one of the the power line via a capacitor, the bases of said transistors being connected to the output of a control comparator capable of take a first state when the voltage of the power line is greater than a predetermined value and a second state when the power line voltage is less than this value predetermined, so that when the output of said comparator goes to its first state, said poles are connected through a said transistors, said coil and said capacitor, the pulse electrical supply being delivered to this coil during the charging of this capacitor, and that when the output of said comparator passes to its second state, the charged capacitor discharges through said coil and the other transistor, the electrical pulse being delivered to this other coil during the discharge of said capacitor.

According to another variant of the invention, the detection device comprises preferably another capacitor for storing electrical energy from the electrical line, this capacitor being mounted so as to discharge in case of interruption of the latter and being connected to an input of said comparator, so that when the voltage delivered by the other capacitor passes below said predetermined value after one delay time with respect to the instant of the cut, said comparator to his second state.

• la figure 1 représente une première variante d'un dispositif de détection selon l'invention ;
• et la figure 2 représente une seconde variante d'un dispositif de détection selon l'invention.

The present invention will be better understood in the study of devices for detecting a telephone line cutoff, described by way of nonlimiting examples and illustrated in the accompanying drawing in which:

• FIG. 1 represents a first variant of a detection device according to the invention;
• and FIG. 2 represents a second variant of a detection device according to the invention.

Referring to Figure 1, we see that we have represented a device 1 for detecting the interruption of a power line by a telephone line comprising two electric wires respectively representing a positive pole (+) 2 and a pole of mass 3.

The device 1 comprises a bistable relay 4 which comprises a movable member 5 of change of state may occupy a first stable position in which it connects a common stud 6 to a first contact pad 7 and a second stable position in which it connects the common stud 6 to a second contact pad 8.

The relay 4 further comprises a first coil 9 and a second coil 10 which, when respectively traversed by an electric current, allow to pass the movable member 5 respectively at its first position in contact with the first stud 7 and at its second position in contact with the second stud of contact 8.

Device 1 also includes a first and a second transistors 11 and 12 and a capacitor 13 for storing energy electric, which are mounted in the following manner.

The collector of transistor 11 is connected to pole (+) 2 via the coil 9 and a current limiter 9a, and its transmitter is connected to the emitter of the transistor 12 and to the ground pole 3 via the capacitor 13. The collector of transistor 12 is connected to the pole of mass 3 via the coil 10. The bases of the transistors 11 and 12 are interconnected and are connected to the output of a comparator 14 via a resistor 15.

An input of the comparator 14 is connected to a circuit 16 delivering a signal corresponding to a reference voltage. His other input is connected to the (+) pole 2 via a resistor 17 and a transistor 18, to the earth pole 3 via a resistor 19 and at the output of the comparator 14 via a resistor 20.

Moreover, the common point between resistance 17 and transistor 18 is connected to the ground pole 3 via a capacitor 21.

The device 1 further comprises an amplifier 22 whose inputs are respectively connected one to the ground pole 3 via a resistor 23 and the other to the circuit 16 delivering the voltage signal of reference and whose output is connected to the base of transistor 18 via a Zener diode 24 and at its input connected to the resistor 23 via a resistor 25, the base of the transistor 18 being moreover connected to the pole (+) 2 via a resistor 26.

The comparator 14, the reference 16 and the amplifier 22 are powered via the common point between the resistor 17, the capacitor 21 and the transistor 18.

Furthermore, the common stud 6 and the contact pads 7 and 8 of relay 4 are respectively connected to a receiver circuit 27, outside the detection device 1 and likely to exploit the electrical signals resulting from the position of the movable member 5.

We will now describe the operation of the device of detection 1, considering for example that in current operation and normal, the minimum voltage of the telephone line 2, 3 is the order of five volts and that in the state of rest, this voltage is of the order forty-eight volts.

When the telephone line 2, 3 is switched on, the Voltage across capacitor 21 increases through transistor 18 biased by the resistor 26. This voltage is limited, for example to 3.6 volts, thanks to the regulator composed of the amplifier 22 and the zener diode 24.

The output of the comparator 14 is in its "high" state. In Consequently, the transistor 12 is blocked and the transistor 11 is driver. A current flows through the first coil 9, the transistor 11 and capacitor 13 which charges. This current produces an electrical pulse in coil 9 that lasts until the capacitor 13 is loaded, for example at most a few hundredths second. This electrical pulse causes the actuation of the movable member 5 of the relay 4 so as to bring it to its first position in contact with the first contact pad 7 of this relay or the keeps in this position. When the capacitor 13 is charged, the current does not pass anymore.

At the cutoff of the telephone line 2, 3, the voltage at capacitor terminals 21 decreases slowly by the fact that this capacitor 21 is discharged by feeding in particular the comparator 14, the reference circuit 16 and the amplifier 22. When this voltage reaches a predetermined value corresponding to the threshold set by the reference circuit 16, for example after about a minute, the output of the comparator 14 changes state and goes to its "low" state. It result that the transistor 11 is blocked and that the transistor 12 becomes driver. Then the capacitor 13 discharges through the coil 10 via transistor 12, producing an electrical pulse which causes the actuation of the movable member 5 of the relay 4 to do so move from its first aforementioned position to its second position in contact with the second contact pad 8 of this relay.

The delay in this activation of relay 4 is mainly determined by the characteristics of the capacitor 21, which can be scheduled to set a time lag of about one minute. This offset allows to maintain the movable member 5 of the relay 4 to its first position in case of breaks in the telephone line 2, 3 of duration, resulting in particular from the transmission by this telephone line of digital signals including "zeros" of voltage.

The detection device 1 also has the advantages following.

A diode bridge rectifier assembly placed on the line telephone 2, upstream of the device 1, makes it possible to overcome the polarity of the telephone line 2, 3. The differential mounting allows to protect the detection device 1 against overvoltages which could be due for example to lightning.

The amplifier 22 amplifies the reference voltage provided by the reference circuit 16. The zener diode 24 introduces a voltage of offset to cancel the base-emitter voltage of transistor 18. The components can be chosen to obtain a voltage of 3.6 volts. Transistor 18 serves as ballast and absorbs the gap between the voltage regulated and the voltage of the telephone line 2, 3.

The comparator 22 and the resistors 17, 19 and 20 provide the comparison of tensions.

Transistors 11 and 12, comparator 14, resistor 15, the voltage of the telephone line 2, 3 and the voltage of the capacitor 13 constitute the control means of the bistable relay 4.

The capacitor 21 ensures the time difference between the instant of the cut of the telephone line 2, 3 and the moment of the change state of relay 4 during this break.

It follows from the foregoing that the detection device 1 proposed works without external power supply and does not use that the electrical energy delivered by the telephone line 2, 3 of a on powering up this line and on the other hand when cuts of this line thanks to the storage of electrical energy in the capacitor 13 producing the activation pulse of relay 4 after cutting off the telephone line 2, 3 and the capacitor 21 which ensures the delay of this actuation.

Referring now to Figure 2, we see that the detection device 28 shown is different from that described in reference to FIG. 1 in that the coils 9 and 10 are suppressed, the collector of the transistor 11 being connected to the pole 2 of the telephone line through the current limiter 9a and the collector transistor 12 being directly connected to the pole 3 of the line telephone, that the common transmitters of transistors 11 and 12 are connected to the pole 3 of the telephone line through a coil 29 and of a capacitor 30 for storing electrical energy, this coil 29 being placed in the vicinity of the movable member 5 of the relay 4.

This detection device 28 functions as the device detection 1.

Indeed, when powering up the telephone line 2, 3, under the effect of the comparator 14 which makes the transistor 12 is blocked and that the transistor 11 is on, a current flows through the transistor 11, coil 29 and capacitor 30 which charges. This current produces an electrical impulse that lasts until this capacitor be charged. This electrical impulse causes the actuation of the movable member 5 of the relay 4 so as to bring it to its first position in contact with the first contact pad 7 of this relay or hold it in this position. When capacitor 30 is charged, the current no longer passes.

At the break of the telephone line 2, 3, under the effect of comparator 14 which makes the transistor 11 goes to its off state and the transistor 12 becomes on, the capacitor 30 discharges at the through the coil 29 via the transistor 12, producing a pulse electric which causes the actuation of the movable member 5 of the relay 4 to move it from its first position above to its second position in contact with the second contact pad 8 of this relay.

The present invention is not limited to the above examples described. Many embodiments are possible without leaving the frame defined by the appended claims.

Claims (6)

1. Appliance for detecting an open circuit in an electrical line, in particular a telephone line, characterized in that it comprises a bistable relay (4) comprising a mobile state transition unit (5) capable of being activated by at least one coil (9, 10) and the external connection pins (6, 7, 8) of which are capable of being connected to external means, means (11) of delivering an electric pulse to the said at least one coil when the said electric line is powered up and produced by the electric power of the latter, in order to place the said relay in a first state, and means (12) of delivering an electric pulse to the said at least one coil when the said electric line is in open circuit condition and produced by electric energy storage means (13) charged by the electric line, in order to place the said relay in a second state.
2. Appliance according to Claim 1, characterized in that the said means of delivering an electric pulse when the said line is in open circuit condition comprise means (21) of delaying this electric pulse by a predetermined delay relative to the beginning of an open circuit condition in the electric line and of delivering this electric pulse only if this open circuit condition is maintained for a duration at least equal to the said delay.
3. Appliance according to either one of Claims 1 or 2, characterized in that it comprises control means acting on the said means of delivering the said electric pulses on the basis of the value of the voltage of the said electric line relative to a reference value.
4. Appliance according to any one of the preceding claims, characterized in that the said means of delivering the said electric pulses comprise two transistors (11, 12) whose emitters are interconnected and whose collectors are connected respectively to a terminal of a first and of a second coil (9, 10) corresponding to the said at least one coil, the said emitters being connected to one of the said poles via an electric energy storage capacitor (13) and the bases of the said transistors being connected to the output of a control comparator (14) capable of taking a first state when the voltage of the electric line is greater than a predetermined value and a second state when the voltage of the electric line is less than this predetermined value, the other terminals of the said coils being connected to the poles of the said electric line, so that when the output of the said comparator passes to its first state, the said poles are connected through one of the said first and second coils, one of the said transistors and the said capacitor, the electric pulse being delivered to this coil during the charging of this capacitor, and that when the output of the said comparator passes to its second state, the charged capacitor discharges through the other transistor and the other coil, the electric pulse being delivered to this other coil during the discharging of the said capacitor.
5. Appliance according to any one of Claims 1 to 3, characterized in that the said means of delivering the said electric pulses comprise two transistors (11, 12) whose emitters are interconnected and connected to one terminal of one coil (29) of the said at least one coil and whose collectors are connected respectively to the poles of the electric line, the other terminal of the said coil being connected to one of the poles of the electric line via a capacitor (30), the bases of the said transistors being connected to the output of a control comparator (14) capable of taking a first state when the voltage of the electric line is greater than a predetermined value and a second state when the voltage of the electric line is less than this predetermined value, so that when the output of the said comparator passes to its first state, the said poles are connected through one of the said transistors, the said coil and the said capacitor, the electric pulse being delivered to this coil during the charging of this capacitor, and that when the output of the comparator passes to its second state, the charged capacitor discharges through the said coil and the other transistor, the electric pulse being delivered to this coil during the discharging of the said capacitor.
6. Appliance according to one of Claims 4 and 5, characterized in that it comprises another capacitor (21) for storing electric energy of the electric line, this capacitor being fitted in such a way as to discharge in the event of an open line condition in the line and being connected to an input of the said comparator such that, when the voltage delivered by the other capacitor falls below the said predetermined value at the end of a delay period relative to the moment of entering the open line condition, the said comparator passes to its aforementioned second state.

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